Here - Meta Marketing e Eventos

22 nd Salt Water Intrusion Meeting: Salt Water Intrusion in Aquifers: Challenges and Perspectives45 mmMODELLING OF SALTWATER INTRUSION: A NEW FULLY COUPLED SURFACE-SUBSURFACE APPROACHJie Yang 1 ; Thomas Graf 1 ; Maria Herold 2 ; Thomas Ptak 2yang@hydromech.uni-hannover.de1 - Institute of Fluid Mechanics and Environmental Physics in Civil Engineering, LeibnizUniversität Hannover, Germany;2 - Geosciences Center, University of Göttingen, GermanyAppelstr. 9A, 30167 Hannover, GermanyAbstract. Coastal aquifers are complex hydrologic systems due to interactions between theocean and adjacent coastal aquifer such as (i) variably saturated flow, (ii) spatial-temporalfluid density variations, (iii) tidal fluctuations, (iv) storm surges overtopping dykes, and (v)surface runoff of storm water. To numerically simulate coastal flow dynamics, a coupledsurface-subsurface approach is presented. The new approach is implemented into theHydroGeoSphere model (Therrien et al. (2010)) and accounts for all processes listed above.The new approach uses the diffusive wave approximation of the St. Venant equation todescribe surface flow. Surface flow and salt transport are fully coupled with subsurfacialvariably saturated, variable-density flow and salt transport through mathematical terms thatrepresent exchange of fluid mass and solute mass, respectively. Both tides and storm surgesinduce a time-variant head that is applied to nodes of the surface domain. The approach isapplied to real cases of tide and storm surge events. Results of a tide simulation show that, inaddition to the classical salt wedge, an extra plume is formed beneath the upper part of theintertidal zone. Monitoring the exchange fluid flux rates through the beach indicates that themajor inflow to the aquifer takes place at the upper part of the intertidal zone, which explainsthe formation of the extra plume. Results also demonstrate that the extra plume ispredominantly being formed during rising tides. Results from a storm surge simulation showthat plume fingers develop below the flooded land surface. The natural remediation byseawards flowing freshwater is relatively slow. Thus, reducing the TDS concentration in theaquifer down to drinking water standards can take up to 10 years.Keywords: saltwater intrusion, coupled approach, tide, storm surge184